In various processes/operations and in day-to-day life, a number of substances including hazardous or non-hazardous chemicals are required to be delivered in the precisely measured doses.
Attempts by the packaging industry has been to develop approaches to evolve accurate delivery systems for active materials especially those that are expensive or are environmentally sensitive or have possibilities of reacting with other ingredients in formulations. There have been several attempts in the past to either encase or laminate or package different materials in water-soluble films (WSF).
The objective of delivering precise quantities of products like detergents has been addressed by the industry for example by packaging detergents in “soluble” and “non-soluble” sachets in dosages ranging from 20 gms/sachet to 50 gms/sachet. In case of non-soluble sachets the detergents tend to adhere to statically charged packaging material surface thereby inhibiting their total transfer to the point of application. Similar problems of particles adhering to statically charged surface are faced when small and precise quantities of pesticides actives are to be packed in non soluble sachets. In the case of soluble sachets problem arising out of chemical reaction of the ingredients to the film cause serious problems in its smooth applications. Similarly in the case of pesticide packaging the active ingredients in the package varies from about 2% to about 30% based on the formulation.
U.S. Pat. No. 4,416,791 discloses a packaging film comprising a base film of at least partially water-soluble plastics material carrying on one surface only a protective layer, in particulate form, of an inert plastics material having a contact angle to water of at least 80.degree, the said layer being effective to protect the base film surface from attack by aqueous media. Such a packaging film has the advantages that, on its unprotected side, it can be dissolved away, or partly dissolved and partly dispersed, by water, whereas on the side carrying the protective layer it is protected from attack by aqueous systems and other aggressive media. It is essential that the inert protective layer be in the form of substantially un-coalesced discrete particles attached firmly to the base film but only loosely or not at all to each other, so that if the base film is dissolved away the protective layer has little or no integrity and is rapidly dispersed. Further it provides a package comprised of the packaging film defined above, having the protective layer on its internal surface(s), so that the layer protects the package from attack by any water present inside the package. It is claimed that such a product can be used to package liquid or solid detergent useful for dosing into domestic or commercial washing machines.
In one of the methods described in the patent a cold-water-soluble polyvinyl alcohol/polyvinyl acetate film having a thickness of 0.0038 cm was heated to a temperature just above its glass transition temperature to render it slightly tacky. Polytetrafluoroethylene powder is sprinkled onto the upper surface of the heated film. The film is then passed between rollers heated and then allowed to cool.
The limitation of U.S. Pat. No. 4,416,791 is that it requires a pre formed WSF substrate and the extent of coating of the Polytetrafluoroethylene powder would be restricted to the surface of the WSF. By this process it would not be possible to control the depth to which the Polytetrafluoroethylene powder can be embedded.
The end use of this invention would be limited to the water repelancy and the release properties of Polytetrafluoroethylene powder on the surface of the pre formed WSF.
U.S. Pat. No. 4,176,079 discloses an invention for dispersing an enzyme into water soluble resin and forming the resin by casting or extruding into a sheet. The sheet is then dried, if necessary, and, if required, cut into “ribbons” for incorporation into the detergent product. The ribbons of enzyme-dispersed resin may be admixed with a detergent composition in granular, viscous liquid, paste or gel form. The resulting mixture may be used directly in the washing process, particularly in an automatic dishwasher, or it may be incorporated within a water-soluble packet, for easy and convenient dispensing. In this case the water soluble resin is being used as a means to bind the enzyme to its matrix. This method of preparing the ribbons also suffers from the shortcoming that two or more reacting substances cannot be dispersed in the same film as they would interact with each other and degrade.
U.S. Pat. No. 6,378,274 discloses a process for producing a thermoformed package of the type comprising the steps of placing a first sheet of formable film over a forming die having a cavity, moulding the film into the cavity thereby forming a recess in the film, placing a composition in the thus formed recess, and sealing a second sheet of film across the recess to close the package. In particular, the prior art relates to such a process for producing a water-soluble package containing a detergent composition. The disclosure is restricted thermo formed packages formed out of a combination of soluble and insoluble films. It also needs pre formed films to be operated on offline equipment for packaging applications thereby making the process of incorporating the materials within the films very complex and requiring expensive equipment.
Patent No. EP 0493553 relates to a containerization system and to containers which are particularly suitable for storing, packaging and transporting toxic or hazardous products, such as agricultural chemicals. The containerization system comprises the chemical in the form of a gel, which is contained within a water soluble or water-dispersible bag. This EP '553 has limitations as it is restricted to toxic products that can be converted into gels and then packaging of gel into a WSF bag.
Patent No. EP 0347220B1 relates to a package comprising e.g. a liquid chemical or a chemical dissolved or dispersed in an organic liquid contained in an envelope of water-soluble or water dispersible material and having a water-soluble or water dispersible seal. The patent also provides a process for the preparation of a package according to the invention which comprises heat sealing the envelope material to obtain a water dispersible or, preferably, a water soluble heat seal. This prior art specifically discusses packaging of pesticides by means of an efficient heat seal system into a container.
Patent GB 2244258B relates to a package comprising hazardous chemical dissolved or dispersed in a liquid or gel which is contained in an envelope of water-soluble or water-dispersable material. The patent seeks to provide a new container system for agrochemicals which is safe to handle. This patent also provides a package which comprises a hazardous chemical dissolved or dispersed in a liquid or gel contained in a water-soluble or water-dispersible laminated film. There is also discussed the delivery of toxic and hazardous materials by means of plain and laminated soluble sachets.
It would be evident from the above state of the art that none of the prior art teach or provide for delivery of the encased, laminated or packaged material in precise quantities. It is therefore the long-standing need of industry to develop efficient and cost effective stable embedded WSFs for controlled dosing in diverse applications and especially to embed a wide variety of substances avoiding interaction with each other within films. Further the need for carriers that can selectively carry combination of materials with dissimilar properties such as miscible/in-miscible, hydrophobic/hydrophilic ingredients continues to elude the industry.